Abdominal aortic aneurysms develop when the wall of the aorta in the abdomen weakens, causing it to bulge and form a balloon-like expansion. When the abdominal aorta reaches a diameter at least 1.5 times the normal size, or greater than 3 cm in total, it is called an abdominal aortic aneurysm (AAA).
The increased stress on the aortic wall may eventually cause the AAA to rupture (burst). The subsequent internal bleeding is frequently fatal before emergency repair can be attempted. When people have emergency repair for rupture, up to half will not survive to leave hospital.
There is a long period of growth before an AAA ruptures. The rate of growth may depend on a number of factors, including increasing age, smoking, blood pressure and a family history of aneurysm.
Most AAAs are asymptomatic, and they are often diagnosed opportunistically during clinical examination or investigation for another condition. Because of this it is difficult to establish their prevalence. There is a national screening programme which enrols men at age 65 and suggests a prevalence of about 1.3% in this population. The prevalence is falling.
The prevalence of AAAs is approximately 6 times lower in women, but the rate of aneurysm rupture is significantly higher. The guideline committee carefully considered the impact of their recommendations on women during guideline development.